1. Field of the Invention
The present invention relates to an organic EL device, and more particularly to an organic EL device provided with a sealing member for sealing a lower electrode, an organic EL layer and an upper electrode.
2. Description of the Related Art
FIG. 2 is a perspective view of an conventional EL display panel 25 provided with an organic EL device. In the EL display panel 25, a plurality of strip-shaped transparent electrodes 11 of ITO (Indium Tin Oxide) (hereinafter referred to as an ITO transparent electrode(s)) are arranged on a glass substrate 2 in a direction of arrow 93. Above the ITO transparent electrodes, a plurality of strip-shaped organic layers 12 are arranged in a direction of arrow 94. A plurality of strip-shaped upper electrodes 13 are superposed on the organic layers 12, respectively.
FIG. 3 is a sectional view of the conventional EL display panel 25, taken in line Ixe2x80x94I in FIG. 2. As seen from FIG. 3, the ITO transparent electrodes 11 as a lower electrode, organic EL layers 12 and upper electrodes 13 are covered with and sealed by a cap 15 on the glass substrate 2. The cap 15, which is made of metal or glass, is secured to the glass substrate 2 by adhesive. The internal space 17 of the cap 15 is filled with nitrogen.
Generally, deposition of impurities such as moisture on an organic EL device greatly changes a device characteristic. This largely attenuates reliability of the organic EL device. In order to over come such an inconvenience, an adsorbent 16 of barium oxide is provided within the cap 15 to adsorb the impurities such as moisture.
In the EL display panel 25, when a voltage is applied between a prescribed ITO transparent electrode 11 and a prescribed upper electrode 13, an organic EL layer 12 located at an area where these electrodes are overlapped, emits light. Therefore, by controlling selection of each ITO transparent electrode 11 and each upper electrode 13, a desired display can be realized using the EL display panel 25.
The above conventional organic has the following defects. Sealing by the cap 15 requires for the cap 15 to be formed in a prescribed shape. This leads to poor efficiency and high cost in manufacturing.
Particularly, when the cap 15 of metal is used, the upper electrode 14 and cap 15 must be kept into non-contact with each other. Therefore, in order to secure the cap 15 on the glass substrate 2, it must be adjusted in position and thereafter bonded to the glass substrate 2. This leads to poor efficiency and high cost in manufacturing. Further, in order to assure the non-contact between the upper electrode 13 and the cap 15, an insulator such as an insulating material or space (e.g. space L1 shown in FIG. 3) must be located therebetween. This impedes the thin-profiling of the organic EL device.
Further, provision of the adsorbent 16 within the cap 15 further impedes thin-profiling of the organic EL device. In addition, the provision of the adsorbent 16 results in poor workability and high cost in manufacturing.
A first object of the present invention is to provide an organic EL device which can provide high efficiency of manufacturing, reduce production cost, obtain great reliability and realize thin-profiling.
A second object of the present invention is to provide a method of manufacturing such an organic EL device.
In order to attain the above first object, in accordance with the present invention, there is provided an organic EL device comprising: a lower electrode formed on a substrate; an organic EL layer formed on the lower electrode; an upper electrode formed on the organic EL layer; a sealing member for sealing the upper electrode, organic EL layer and upper electrode on the substrate so that they are covered with the sealing member, wherein the sealing member is made of an aluminum material coated with an insulating layer in its inner surface.
In this configuration, since the sealing member is made of an aluminum material coated with an insulating layer in its inner surface, contact of the aluminum material with the upper electrode produces no trouble. Thus, such a fine alignment as required in sealing by a metallic cap is not required, thereby improving working efficiency and reducing the production cost. Further, any insulator for assuring non-contact between the aluminum material and the upper electrode is not required so that the organic EL device can be formed in a thin-profile style. In addition, the aluminum foil is so flexible that it can be deformed freely, thereby improving working efficiency and reducing the production cost.
Preferably, the aluminum material is a flexible aluminum sheet. Therefore, it is not necessary to form the aluminum material in a prescribed shape in advance, thereby improving working efficiency and reducing the production cost.
Preferably, the insulating layer is an aluminum oxide layer formed by anodic oxidation of the aluminum material. Since the surface of such an-oxide layer is porous, impurities can be taken into a large number of pores of the anodic oxide layer, thereby improving the reliability of the organic EL device. This oxide layer has both functions of insulation and absorbing the impurity such as moisture. For this reason, it is not necessary to provide an insulator and an impurity absorbing member individually, thereby providing a thin-profile EL device and improving working efficiency and reducing the production cost.
Preferably, the insulating layer is a porous aluminum oxide layer. Since such a porous oxide layer can have a function of xe2x80x9cgetteringxe2x80x9d of taking impurities into a large number of pores, it can take the impurities internally generated during use, thus lengthening the life of the organic EL device.
Preferably, the aluminum sheet is formed in such a manner that a surface of the aluminum oxide layer is subjected to gas flow-out treatment in vacuum, and thereafter the lower electrode, organic EL layer and upper electrode are sealed on the substrate in an atmosphere of inert gas.
In this configuration, the surface of the aluminum oxide layer is subjected to gas flow-out treatment, and the lower electrode, organic EL layer and upper electrode are sealed on the substrate by the sealing member. Therefore, gas can be caused to flow out from the large number of pores of the aluminum oxide layer so that the impurity can be taken into the pores, thereby improving the reliability of the organic EL device. In order to attain the second object, in accordance with the present invention, there is provided a method of manufacturing an organic EL device comprising the steps of: forming a lower electrode formed on a substrate; forming an organic EL layer on the lower electrode; forming an upper electrode on the organic EL layer to provide the organic EL device; preparing an aluminum material coated with an insulating layer in at least its inner surface; and sealing the organic EL device so that it is covered with the aluminum material.
In the manufacturing method, preferably, the step of preparing the aluminum material comprises the steps of: making anodic oxidation to form an aluminum oxide layer on a surface of a flexible aluminum sheet; and removing gas contained within the aluminum oxide layer, and the step of sealing the organic EL device comprises the step of: fixing the aluminum sheet with the gas removed on a surface of the substrate in an atmosphere of inert gas or in vacuum.
In the manufacturing method, preferably, the step of removing gas is to heat the aluminum sheet with the aluminum oxide layer for several xe2x88x9260 minutes at 60-300xc2x0 C. in vacuum.
In the manufacturing method, preferably, the step of making anodic oxidation is to form a porous aluminum oxide layer; and the step of removing gas is to heat the aluminum sheet in vacuum so that impurities contained in pores of the porous aluminum oxide layer are discharged.
In the manufacturing method, the step of sealing the organic EL device comprises the steps of: mounting the organic EL device and aluminum sheet in a sealing chamber and once heating them at room temperature xe2x88x92150xc2x0C. in vacuum; introducing inert gas into the sealing chamber; and fixing the aluminum sheet on the substrate through an adhesive and heating it.
In the manufacturing method, preferably, the inert gas is argon gas.
The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings.